Critical power consuming systems which require an uninterrupted power supply are commonly connected to at least two redundant power supply sources. It is typically the case that one of the power supplies is a primary power supply and all other power supplies are backup power supplies provided in case the primary power supply fails or otherwise becomes incapable of providing the necessary power to the power consuming system. Redundant power supplies are very common in many medical applications, such as ventilators, since breath delivery may depend upon power being continuously provided to the power consuming system. Redundant power supplies are also common in many other mission critical applications such as computing applications, database applications, refrigeration systems, and so on.
Prior and existing redundant power supply designs utilize discrete diodes to isolate different power sources that are connected to a common power bus. As can be seen in FIG. 1, each power source 104a, 104b in a redundant power supply system 100 generally has its own discrete diode 108a, 108b, respectively, that controls the amount of power provided by each source 104 to the power consuming load 116. A capacitor 112 may also be connected in parallel across the load 116 to provide temporary power to the bus and hence to the load 116.
The discrete diodes 108 serve to avoid short circuits between power supplies 104a, 104b and also protect the load 116 from reversed polarity. If one of the power supplies 104a fails, the load 116 can continue to operate with power supplied from the other power supply 104b without a power interruption.
While this solution is popular and has been used in many power consuming systems, there are several disadvantages to utilizing the discrete diodes 108. First of all, the diodes 108 dissipate a non-trivial amount of power. This causes the overall efficiency of the system 100 to decrease due to the losses realized in the diodes 108. Additionally, since the diodes 108 dissipate so much power they also generate heat. This creates a need for attaching heat sink devices to the diodes 108 to help cool the diode 108 in systems that deliver significant power. Without the heat sink devices, the diode 108 could overheat and become inoperable, thereby jeopardizing the entire system 100.